Fixed a few bugs in ARM disassembly and added more testing stuff to test_arm.c

* added a way to test what should be invalid instructions
* added a way to test what should be valid instructions

* fixed and added a test for a thumb-2 invalid sequence that was incorrectly allowed before these changes (pop.w with sp argument included)
* fixed and added a test for a blx from thumb to ARM that had its immediate argument incorrect (misaligned)

* eliminated some warnings by explicitly casting so I could turn on
  treat warnings as errors locally

* general notes: probably worth turning on treat all warnings as errors in the msvc project files, had a subtle bug that resulted from a missing declaration causing differences in dll and static compilation modes

( code was working incorrectly in dll form because of missing declaration in arch/ARM/ARMMapping.h for new function ARM_blx_to_arm_mode. Something about the linking was confusing ld when making the dll, and the resulting offsets were wonky (e.g. the added ble test would show up as #0x1fc instead of #0x1fe like it should have )